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Harvard Forest Data Archive
Tree Growth in Macrosystems Biodiversity Project at Harvard Forest 2011-2013Related Publications
- Lead: Brian Enquist, Robert Waide, James Brown
- Investigators: Vanessa Buzzard
- Contact: Brian Enquist
- Start date: 2011
- End date: 2013
- Status: completed
- Location: Harvard Forest
- Latitude: +42.53731 to +42.54088
- Longitude: -72.17865 to -72.17473
- Elevation: 352 to 363 meter
- Taxa: Acer pensylvanicum, Acer rubrum, Amelanchier laevis, Betula alleghaniensis, Betula lenta, Betula papyrifera, Castanea dentata, Fraxinus americana, Hamamelis virginiana, Ilex verticillata, Kalmia latifolia, Nyssa sylvatica, Picea abies, Picea rubens, Pinus hartwegii, Pinus strobus, Prunus serotina, Quercus rubra, Rhododendron prinophyllum, Vaccinium corymbosum, Viburnum alnifolium, Tsuga canadensis
- Release date: 2015
- EML file: knb-lter-hfr.264.2
- DOI: digital object identifier
- EDI: data package
- DataONE: data package
- Related links:
- Project Website
- Soil Bacteria and Archaea in Macrosystems Biodiversity Project at Harvard Forest since 2012
- Soil Chemistry and Moisture in Macrosystems Biodiversity Project at Harvard Forest since 2012
- Soil Invertebrate Species in Macrosystems Biodiversity Project at Harvard Forest since 2012
- Soil Temperature and Water Content in Macrosystems Biodiversity Project at Harvard Forest since 2011
- Study type: short-term measurements
- Research topic: biodiversity studies; international research projects; regional studies
- LTER core area: primary production, populations, organic matter
- Keywords: biodiversity, growth, transects, tree growth, species lists
Patterns of biodiversity, such as the increase toward the tropics and the peaked curve during ecological succession, are fundamental phenomena for ecology. Such patterns have multiple, interacting causes, but temperature emerges as a dominant factor across organisms from microbes to trees and mammals, and across terrestrial, marine, and freshwater environments. However, there is little consensus on the underlying mechanisms, even as global temperatures increase and the need to predict their effects becomes more pressing.
The purpose of this project is to generate and test theory for how temperature impacts biodiversity through its effect on biochemical processes and metabolic rate. A combination of standardized surveys in the field and controlled experiments in the field and laboratory measure diversity of three taxa -- trees, invertebrates, and microbes -- and key biogeochemical processes of decomposition in seven forests distributed along a geographic gradient of increasing temperature from cold temperate to warm tropical.
This dataset contains annual growth measurements of trees along a series of transects using the measures of diameter at breast height and/or diameter and ground height at the five Gentry plots set up at Harvard Forest. These plots were set up by the Enquist Lab (PI, Brian Enquist) from the University of Arizona as part of a macrosystems biodiversity and latitude project supported by the National Science Foundation under Cooperative Agreement DEB#1065836.
Annual measurements within each Gentry plot
We use a revised CTFS protocol to measure stems within each 2 x 100m transect (Condit 1998).
Determining which individuals are within the transect
General rule: If the center of the plant’s base is within the 2m boundary of the line, the plant is within the transect. For example, consider a tree with multiple stems that lies directly on the transect line. If the basal center point for all the stems is within the transect, all stems, including those that lie outside the transect line, are measured. However, if the center point of all stems comprising the individual is outside of the transect, none of the stems are measured, and the individual is considered to be outside of the plot.
There are species-specific cases to this rule:
Ground-skimming conifer branches: Some firs have extensive networks of low-lying branches that dive into and then out of the ground. To avoid retagging the same individuals, we only tag firmly-rooted, vertical stems.
Junipers: We associate large clumps of bush like junipers as single individuals. As with all ground measurements, we only measure and tag the largest stem of each individual.
Determining separate individuals
Stems are considered to be part of the same individual if there are above or belowground connections among multiple stems. Belowground connections can be checked by minor digging, but no deeper than one fingers-length, (approx. 10cm). We also assume that there are belowground connections if all stems appear to emerge from a single location, i.e. the angle at which each stem emerges from the ground points to a central location of germination for the individual. Multiple stems are denoted as a single individual by recording the largest stem or “main stem” tag number with the tag numbers of each secondary stem.
Determining if and where to measure
General rule: Measure DBH (diameter at breast height) for all stems greater than or equal to 1cm diameter at 1.3m from the ground. Measure DGH (diameter at ground height) for all stems below 1cm DBH, but greater than or equal to 1cm basal diameter at the ground.
Always measure DBH at 1.3m from on the upslope side of the individual.
If scars or any malformations occur at 1.3m, move the DBH measurement above or below 1.3cm.
If a tree is buttressed, measure 1.3cm from the top of the buttress.
If a stem has bends and curves, measure 1.3m from ground including curvature, i.e. do not measure vertically, but rather measure 1.3m along the stem.
Measure DGH from the lowest accessible point on the stem without major alterations to the natural environment, i.e. do not dig up litter extensively or move debris. If the individual has multiple stems, only measure the largest stem.
Lianas, Vines and hemi-epiphytes are measured if the original rooting point is in the transect, and live stems are found climbing into the canopy.
Painting: Use white or orange tree paint to mark where DBH measurements were taken on trees, shrubs, and vines.
Note: some sites do not allow tree paint (Luquillo and BCI), in which case, carefully notated descriptions will be used for re-measurement. Notations include:
POM (point of measurement): distance in cm from the ground to the location of diameter measurement. Note if different from 130 cm.
DTN (distance to nail): distance in cm from location of diameter measurement to the nail used to tag the individual. Value will be positive if nail is above POM, and value will be negative if nail is below POM. Nails should always be 20cm from point of measurement.
Palms: Measure a single DBH for palms that have woody trunks at 1.3m from ground.
For all other palms, take three measurements: DGH, diameter at highest point of woody stem (see below), and distance from ground to the highest diameter measurement. The woody stem is defined as any part of the palm stem that is below the location of where fronds separate from the main stem.
Large herbs: With large herbs, always measure a ground measurement of the largest stem (frond, petiole, etc.) in a clump. Examples include ginger, heliconia, ferns, devil’s club, etc.
Tagging each stem
All trees above 5cm DBH are tagged 20 cm above the point of measurement (POM, 1.3m) by nailing a tag to the tree with an aluminum nail. All stems below 5cm DBH are tagged by tying a tag to the stem with either metal wire. We nail the tags to each tree so that the nail has a downward angle to ensure the tag falls away from the stem. We do not drive nails very deeply into the tree to allow for several years of growth. We use enough wire to allow for ~5 years of potential growth. Tags that are attached too tightly can constrict growth or cause the tree to swallow the wire. All tags are placed on the stem containing the POM, i.e. above live branches but below the POM, and below live branches above the POM. This ensures that the measurement is taken on the tagged stem.
Palms can be nailed, but need to also have grafting tape run through the tag and tied around the trunk.
Some trees cannot be nailed regardless of their size, examples include Cecropia and Schefflera.
Herbaceous clumps are tagged with grafting tape that encompasses the entire individual, not just a single stem.
Note: Trees above 1cm DBH that were previously tagged are not retagged. This reduces confusion that may occur by adding new tags to individuals with existing tags, especially at sites that currently follow CTFS protocol.
Checking the measurements
As with any large resampling, there are always mistakes. To minimize mistakes that make it into each year’s resampling data, we thoroughly look over the data sheet for mistakes before leaving each site. Some common mistakes include not recording measurements, missed species ids, misplaced measurements (i.e. recording a DBH instead of a DGH), etc. We attempt to find these mistakes by carefully looking over each measurement. When a mistake is found, we highlight the row corresponding to the stem from which the mistake may have occurred. We are then able to assess these errors by returning to the field to confirm/remeasure any stems under question.
This dataset is released to the public under Creative Commons license CC BY (Attribution). Please keep the designated contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement.
Enquist B, Waide R, Brown J. 2015. Tree Growth in Macrosystems Biodiversity Project at Harvard Forest 2011-2013. Harvard Forest Data Archive: HF264.
hf264-01: hf macroplots tree growth
- sample.id: unique identification number of the sample
- site: full name of the experimental site where the reading was taken
- plot.code: plot code as defined by the three letter site code (HFR = Harvard Forest LTER) plus the letter "T" to define Gentry tree plots 1-5. (e.g. Gentry plot 1 at Harvard Forest LTER is HFRT1)
- date: date when measurements were first taken for each stem
- year2.date: year 2 date when measurements were made for each stem
- year3.date: year 3 date when measurements were made for each stem
- project.year: year of the project that the stem was first measured (unit: number / missing value: NA)
- latitude: latitude of sampling plot taken in the center of each Gentry plot using a handheld GPS Garmin 62stc (estimated position error of 5-10m) and converted to decimal with a WGS84 projection (unit: degree / missing value: NA)
- longitude: longitude of sampling plot taken in the center of each Gentry plot using a handheld GPS Garmin 62stc (estimated position error of 5-10m) and converted to decimal with a WGS84 projection (unit: degree / missing value: NA)
- elevation: longitude of sampling plot taken in the center of each Gentry plot using a handheld GPS Garmin 62stc (estimated position error of 5-10m) and converted to decimal with a WGS84 projection and converted to meters (unit: meter / missing value: NA)
- line: each Gentry plot has ten 50 meter transects, denoted as lines 1-10. All transect lines are from south to north.
- main.stem: main stem tag number of largest stem of a multi-stemmed individual. Individual stems were tagged and measured separately follow CTFS protocol.
- lter.tag: Long Term Ecological Research tag number. We used the existing tag any time a tree was already tagged in our plots.
- enq.tag: Enquist Lab tag number. Individual stems were tagged and measured separately follow CTFS protocol.
- distance: distance of the plant from the start of the 50 m transect (unit: meter / missing value: NA)
- location.2012: plant location in 2012 determined by dividing the 2 m transect into fifths
and facing north
- LL: left left of the transect
- L: left of the transect
- C: center of the transect
- R: right of the transect
- RR: right right of the transect
- habit: plant life form as determined by the USDA growth habit (usda.gov). All plants listed as Tree Shrub were considered Shrubs.
- morpho: semi-descriptive name used for sample before correct species determination was known
- family: taxonomic family of sample. Matched with family names used in Tropicos.org.
- genus: taxonomic genus of sample. Matched with current genera used in Tropicos.org.
- species: taxonomic species of sample. Matched with species names used in Tropicos.org.
- taxon: full genus and species identifier
- authority: person who originally named and described species
- determiner: person in Enquist lab who identified specimen
- year1.dbh: year 1 diameter at breast height measured using a cloth DBH tape (unit: centimeter / missing value: NA)
- year2.dbh: year 2 diameter at breast height measured using a cloth DBH tape. An X indicates that the stem is dead. (unit: centimeter / missing value: NA)
- year3.dbh: year 3 diameter at breast height measured using small cm DBH tape. An X indicates that the stem is dead. (unit: centimeter / missing value: NA)
- year1.dgh: year 1 diameter at ground height measured using small cm DBH tape. An X indicates that the stem is dead. (unit: centimeter / missing value: NA)
- year2.dgh: year 2 diameter at ground height measured using small cm DBH tape. An X indicates that the stem is dead. (unit: centimeter / missing value: NA)
- year3.dgh: year 3 diameter at ground height measured using small cm DBH tape. An X indicates that the stem is dead. (unit: centimeter / missing value: NA)
- mortality.date: date on which individuals/stems were found dead, if applicable
- error: codes for errors in data and corrections
- a: Mainstem # was forgotten in the data sheet. Corrected by inserting the mainstem # if there were no distance or location measurements and there was a DBH measurement (both indicating that it was a stem and not a new plant).
- b: A secondary stem tag number was not included. Corrected by inserting the missing tag number. Ex. If secondary stems have tag numbers 1,2,3,blank,5,6 in the data sheet, we would insert # 4 for the missing tag number.
- c: The distance of the plant along the 50 m transect was corrected.
- d: The location on the transect for year2 was considerably different from year1's location. Ex. Year1 - Right, Year2 - L or LL; last year - Center, this year - RR or LL. These errors were not corrected because it is unknown which location is correct.
- e: change morpho
- f: A measurement error where 6s were written instead of 9s and vice versa. Corrected by switching the 6 for a 9 or a 9 for a 6. These switches were only made when the following year's measurements verified that this mistake was made the previous year. Ex. Year1 DBH - 9.2, Year2 DBH - 6.3. Year1 DBH would be changed to 6.2
- g: In Year1 the measurement was a DGH, but in subsequent years, it became a DBH because of the change in protocol, therefore it is not necessarily indicative of growth. Year1's protocol stated that a DBH measure of < 2.5 cm was to be measured as a DGH. Year2's protocol stated that only plants with a DBH < 1 cm were to be measured as a DGH
- h: The year 1 measurement was incorrect. Verified in the field by comparing year 1 measurement to year 2 measurement. Not corrected
- i: The year 1 measurement was recorded as a DGH, but it should have been recorded in the year 1 DBH column or vice versa (recorded DBH should be DGH). This was verified in the field in year 2. Corrected by moving the year 1 DGH measurement to the year 1 DBH column in year 2.
- j: Year 1's tag number was recorded incorrectly. Corrected in the filed in year 2 by replacing the incorrect tag number with the correct tag number.
- k: A single stem has 2 tags (1 tag from the LTER site and 1 Enquist tag). Both tag numbers are left in the data sheet.
- l: The stem is within the transect but was not recorded (i.e. forgotten or not included in the year 1 protocol), but is included in year 2.
- m: The species was recorded in the data sheet with only the genus Nyssa. It should have included the species, Nyssa sylvatica. Corrected in the data sheet by including the species.
- n: The species name was accepted by USDA but not tropicos. The species with this error code are the only ones in the data set that do not have approved names from tropicos.
- o: Decimal was forgotten in year 1 measurement. Corrected by verifying the true DBH or DGH in year 2 and then inserting the decimal point for the year 1 measurement.
- p: The stem was recorded in the wrong line number in year 1. corrected by replacing the incorrect line number with the correct one.
- q: After reassessing in year 2, the stem is outside of the transect or should not be measured according to the protocol
- r: The decimal point on a DGH measurement was put in the wrong spot and/or additional numbers were accidentally typed into the PDA. Corrected by moving the decimal or removing a number so that year 2's measurement is close to year 1 measurement. The original measurement for year 2 is recorded in the notes.
- s: At Luquillo on year 2, Seth, an El Verde field tech, helped us identify seedlings from photos we took in the field. If he provided a species code but was still uncertain of the species or failed to identify the species, the row is assigned the error code "s".
- t: If we identified an individual but had uncertainty in its identification, the individual is assigned an error code "t".
- u: If we identified an individual but had uncertainty in its identification, the individual is assigned an error code "t"
- v: The point of measurement in year 1 was much higher than the standard 1.3 meters above ground. Year 2 measurements were taken at 1.3 meters so differences between year 1 and year 2 DBH measurements may not indicate growth.
- w: The year 2 DGH measurement was below 1 cm DGH so the tag was removed from the individual.
- x: changed species identification
- year2.recorder: name of the person who was recording the data
- year2.tagger: name of the person who was tagging new stems
- year2.measurer: name of the person who was taking stem measurements
- year1.notes: year 1 field notes. Often include morpho/multistem and other location information. G=the switch made from measuring all stems <2.5 at DBH at ground to measuring them at DBH if they reach DBH. This follows CTFS protocol.
- year2.notes: year 2 field notes. Often include morpho/multistem and other location information. G=the switch made from measuring all stems <2.5 at DBH at ground to measuring them at DBH if they reach DBH. This follows CTFS protocol.
- year3.notes: year 3 field notes. Often include morpho/multistem and other location information. G=the switch made from measuring all stems <2.5 at DBH at ground to measuring them at DBH if they reach DBH. This follows CTFS protocol.